In microcell power MOSFETs (metal oxide semiconductor field effect transistors) a vertical current flows through transistor cells between the source and drain electrodes placed at the front and back sides of a semiconductor body. In MOSFETs based on trench gate technology the transistor channel is formed along vertical sidewalls of trench gate structures extending from the front side into the semiconductor body. Below the gate structures, field electrodes, which may be electrically connected to the source electrode, decrease the gate to drain capacity and provide a counter charge with respect to a charge resulting from the doping in the drift zone. Smart power semiconductor devices may include signal processing circuits integrated with the transistor cells in the same semiconductor body.
It is desirable to improve reliability and to reduce manufacturing costs of power semiconductor devices.